1
$\begingroup$

I remember back in my high school, when we started electrolysis, I became quite interested in it. I decided to do a home experiment on electrolysis of water. I grabbed my graphite pencils, a glass of water made of steel, two wires and some water. I wrapped the wire on my graphite nibs(on one end) and immersed the other end in water. I connected the wires to 240V AC supply(that was the supply which powers our home.)

Observations:

Initially, bubbles formed on both of the electrodes(I think they must be a hydrogen/oxygen mixture since the cathode and anode switches in between due to ac)

The glass of water became very hot with the passage of time(which was due to resistance heating i suppose)

The interesting part came when I added a few grams of table salt to water. Within seconds, the graphite rods turned red and there were fumes of gas(most probably it was steam cause the fumes were white.) There might have been sparks in the plug as well, but I don't remember for sure. I immediately pulled the plug out before it got any worse.

I didnt try anything of that sort again as i knew i could have done worse than that. But it doesnt cause any harm in knowing what actually happened when I added salt.

Why did the graphite turned glowing red?

What was the composition of those fumes?

What more could have gone worse?

$\endgroup$

closed as too broad by Mithoron, A.K., aventurin, Jon Custer, Todd Minehardt Sep 3 '18 at 20:09

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    $\begingroup$ There are easier ways to kill yourself. $\endgroup$ – Ivan Neretin Sep 2 '18 at 7:18
  • $\begingroup$ @IvanNeretin That I know. What i don't know is: the chemistry behind it. $\endgroup$ – Shah M Hasan Sep 2 '18 at 7:26
1
$\begingroup$

What you are trying to do is called a redox reaction (from REDuction-OXydation) in which one molecule will be oxidized (i.e. give one electron) and another will be reduced (i.e. receive one electron). The propensity of two different molecules to exchange electrons is called "redox potential" and measured in Volts.

In the case of water, its dissociation into hydrogen and oxygen has a potential of 1.23V(1), so a 1.5V battery would be enough (however a rechargeable battery usually has a potential of 1.2V which would not be enough).

In your case, you apply a 240V potential, which will not only promote many other reactions but also heat the water up because of the Joule effect and make it boil.

(1) I purposely ignored the sign not to confuse you.

$\endgroup$
  • $\begingroup$ I am comfortable working with reduction potentials and electrochemistry, but the question was: why did the graphite rod became glowing red within seconds of adding NaCl. It could have glowed red during electrolysis of water but it only did upon adding NaCl. Why? $\endgroup$ – Shah M Hasan Sep 2 '18 at 14:22
  • 1
    $\begingroup$ Adding NaCl will make water MUCH more conductive so the graphite rod will warm up so much (at the surface) it will glow. Actually, very pure water does not conduct electricity at all. Only its impurities do. $\endgroup$ – SteffX Sep 2 '18 at 14:27
  • $\begingroup$ What more could have gone worse? $\endgroup$ – Shah M Hasan Sep 2 '18 at 14:28
  • 1
    $\begingroup$ Not much I think, though adding NaCl and with a 240V potential, you will also make chlorine gas, which is extremely toxic. I really suggest that you don't work with 240V current... or 110V because it can be deadly $\endgroup$ – SteffX Sep 2 '18 at 14:31
  • 1
    $\begingroup$ I am not worried about you. I am worried about science! 😋 $\endgroup$ – SteffX Sep 2 '18 at 14:35

Not the answer you're looking for? Browse other questions tagged or ask your own question.